Production of Diesel Fuel from Biorenewable Feedstocks

ABSTRACT

A process has been developed for producing diesel boiling range fuel from renewable feedstocks such as plant oils and animal oils, fats, and greases. The process involves treating a renewable feedstock by hydrogenating and deoxygenating i.e. decarboxylating, decarbonylating, and/or hydrodeoxygenating to provide a hydrocarbon fraction useful as a diesel boiling range fuel or diesel boiling range fuel blending component. If desired, the hydrocarbon fraction can be isomerized to improve cold flow properties. A portion of the hydrogenated and deoxygenated feedstock is selectively separated and then recycled to the treatment zone to increase the hydrogen solubility of the reaction mixture.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application Ser. No.60/973,788 filed Sep. 20, 2007, the contents of which are herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a process for producing diesel boiling rangehydrocarbons useful as transportation fuel from renewable feedstockssuch as the triglycerides and free fatty acids found in materials suchas plant oils, fish oils, animal fats, and greases. The process involveshydrogenation, decarboxylation, decarbonylation, and/orhydrodeoxygenation and isomerization in one or more reactors. Aselective hot high pressure hydrogen stripper is used to remove at leastthe carbon oxides from the hydrogenation, decarboxylation and/orhydrodeoxygenation zone effluent before entering the isomerization zone.

BACKGROUND OF THE INVENTION

As the demand for diesel boiling range fuel increases worldwide there isincreasing interest in sources other than petroleum crude oil forproducing diesel fuel and diesel fuel blending components. One suchrenewable source is what has been termed biorenewable sources. Theserenewable sources include, but are not limited to, plant oils such ascorn, rapeseed, canola, soybean and algal oils, animal fats such asinedible tallow, fish oils and various waste streams such as yellow andbrown greases and sewage sludge. The common feature of these sources isthat they are composed of glycerides and Free Fatty Acids (FFA). Both ofthese classes of compounds contain n-aliphatic carbon chains having fromabout 8 to about 24 carbon atoms. The aliphatic carbon chains in theglycerides or FFAs can be fully saturated or mono, di- orpoly-unsaturated.

There are reports in the art disclosing the production of hydrocarbonsfrom oils. For example, U.S. Pat. No. 4,300,009 discloses the use ofcrystalline aluminosilicate zeolites to convert plant oils such as cornoil to hydrocarbons such as gasoline and chemicals such as paraxylene.U.S. Pat. No. 4,992,605 discloses the production of hydrocarbon productsin the diesel boiling range by hydroprocessing vegetable oils such ascanola or sunflower oil. Finally, US 2004/0230085 A1 discloses a processfor treating a hydrocarbon component of biological origin byhydrodeoxygenation followed by isomerization.

Applicants have developed a process which comprises one or more steps tohydrogenate, deoxygenate and isomerize the renewable feedstock. Theperformance of the isomerization catalyst is improved by removing atleast carbon dioxide from the feed to the isomerization zone. Thepresence of carbon dioxide or other carbon oxides may result in thedeactivation of the isomerization catalyst. The carbon dioxide isremoved using a selective hot high pressure hydrogen stripper.

SUMMARY OF THE INVENTION

A hydroconversion process for producing an isoparaffin-rich dieselboiling range product from a renewable feedstock wherein the processcomprises treating the renewable feedstock in a reaction zone byhydrogenating and deoxygenating the feedstock at reaction conditions toprovide a first reaction product comprising a hydrocarbon fractioncomprising n-paraffins. The carbon dioxide and water generated asbyproducts in the first reaction zone are selectively removed from thefirst reaction product in an integrated a hot high pressure stripperusing hydrogen as the stripping gas. The hydrogen stripped firstreaction product is introduced to a hydroisomerization reaction zone.The isomerized product is recovered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 and FIG. 2 are schematics of one embodiment of the invention.FIG. 1 is a more simplistic schematic, while FIG. 2 is more detailed.

DETAILED DESCRIPTION OF THE INVENTION

As stated, the present invention relates to a process for producing ahydrocarbon stream useful as diesel boiling range fuel from renewablefeedstocks such as renewable feedstocks originating from plants oranimals. Some of these feedstocks are known as biorenewable fats andoils. The term renewable feedstock is meant to include feedstocks otherthan those obtained from petroleum crude oil. The biorenewablefeedstocks that can be used in the present invention include any ofthose which comprise glycerides and free fatty acids (FFA). Most of theglycerides will be triglycerides, but monoglycerides and diglyceridesmay be present and processed as well. Examples of these feedstocksinclude, but are not limited to, canola oil, corn oil, soy oils,rapeseed oil, soybean oil, colza oil, tall oil, sunflower oil, hempseedoil, olive oil, linseed oil, coconut oil, castor oil, peanut oil, palmoil, mustard oil, cottonseed oil, jatropha oil, tallow, yellow and browngreases, lard, train oil, fats in milk, fish oil, algal oil, sewagesludge, and the like. Additional examples of renewable feedstocksinclude non-edible vegetable oils from the group comprising Jatrophacurcas (Ratanjoy, Wild Castor, Jangli Erandi), Madhuca indica (Mohuwa),Pongamia pinnata (Karanji Honge), and Azadiracta indicia (Neem). Thetriglycerides and FFAs of the typical vegetable or animal fat containaliphatic hydrocarbon chains in their structure which have about 8 toabout 24 carbon atoms, with a majority of the fats and oils containinghigh concentrations of fatty acids with 16 and 18 carbon atoms Mixturesor co-feeds of renewable feedstocks and petroleum derived hydrocarbonsmay also be used as the feedstock. Other feedstock components which maybe used, especially as a co-feed component in combination with the abovelisted feedstocks, include spent motor oils and industrial lubricants,used paraffin waxes, liquids derived from the gasification of coal,biomass, or natural gas followed by a downstream liquefaction step suchas Fischer-Tropsch technology, liquids derived from depolymerization,thermal or chemical, of waste plastics such as polypropylene, highdensity polyethylene, and low density polyethylene; and other syntheticoils generated as byproducts from petrochemical and chemical processes.Mixtures of the above feedstocks may also be used as co-feed components.In some applications, an advantage of using a co-feed component is thetransformation of what may have been considered to be a waste productfrom a petroleum based or other process into a valuable co-feedcomponent to the current process.

Renewable feedstocks that can be used in the present invention maycontain a variety of impurities. For example, tall oil is a byproduct ofthe wood processing industry and tall oil contains esters and rosinacids in addition to FFAs. Rosin acids are cyclic carboxylic acids. Therenewable feedstocks may also contain contaminants such as alkalimetals, e.g. sodium and potassium, phosphorous as well as solids, waterand detergents. An optional first step is to remove as much of thesecontaminants as possible. One possible pretreatment step involvescontacting the renewable feedstock with an ion-exchange resin in apretreatment zone at pretreatment conditions. The ion-exchange resin isan acidic ion exchange resin such as Amberlyst™-15 and can be used as abed in a reactor through which the feedstock is flowed through, eitherupflow or downflow.

Another possible means for removing contaminants is a mild acid wash.This is carried out by contacting the feedstock with an acid such assulfuric, nitric or hydrochloric acid in a reactor. The acid andfeedstock can be contacted either in a batch or continuous process.Contacting is done with a dilute acid solution usually at ambienttemperature and atmospheric pressure. If the contacting is done in acontinuous manner, it is usually done in a counter current manner. Yetanother possible means of removing metal contaminants from the feedstockis through the use of guard beds which are well known in the art. Thesecan include alumina guard beds either with or without demetallationcatalysts such as nickel or cobalt. Filtration and solvent extractiontechniques are other choices which may be employed. Hydroprocessing suchas that described in U.S. application Ser. No. 11/770,826, herebyincorporated by reference, is another pretreatment technique which maybe employed.

The renewable feedstock is flowed to a first reaction zone comprisingone or more catalyst beds in one or more reactors. The term “feedstock”is meant to include feedstocks that have not been treated to removecontaminants as well as those feedstocks purified in a pretreatmentzone. In the reaction first zone, the renewable feedstock is contactedwith a hydrogenation or hydrotreating catalyst in the presence ofhydrogen at hydrogenation conditions to hydrogenate the reactivecomponents such as olefinic or unsaturated portions of the n-paraffinicchains. Hydrogenation and hydrotreating catalysts are any of those wellknown in the art such as nickel or nickel/molybdenum dispersed on a highsurface area support. Other hydrogenation catalysts include one or morenoble metal catalytic elements dispersed on a high surface area support.Non-limiting examples of noble metals include Pt and/or Pd dispersed ongamma-alumina or activated carbon. Hydrogenation conditions include atemperature of about 40° C. to about 400° C. and a pressure of about 689kPa absolute (100 psia) to about 13,790 kPa absolute (2000 psia). Inanother embodiment the hydrogenation conditions include a temperature ofabout 200° C. to about 300° C. and a pressure of about 1379 kPa absolute(200 psia) to about 4826 kPa absolute (700 psia). Other operatingconditions for the hydrogenation zone are well known in the art.

The catalysts enumerated above are also capable of catalyzingdecarboxylation, decarbonylation and/or hydrodeoxygenation of thefeedstock to remove oxygen. Decarboxylation, decarbonylation, andhydrodeoxygenation are herein collectively referred to as deoxygenationreactions. Decarboxylation conditions include a relatively low pressureof about 689 kPa (100 psia) to about 6895 kPa (1000 psia), a temperatureof about 200° C. to about 400° C. and a liquid hourly space velocity ofabout 0.5 to about 10 hr⁻¹. In another embodiment the decarboxylationconditions include the same relatively low pressure of about 689 kPa(100 psia) to about 6895 kPa (1000 psia), a temperature of about 288° C.to about 345° C. and a liquid hourly space velocity of about 1 to about4 hr⁻¹. Since hydrogenation is an exothermic reaction, as the feedstockflows through the catalyst bed the temperature increases anddecarboxylation and hydrodeoxygenation will begin to occur. Thus, it isenvisioned and is within the scope of this invention that all thereactions occur simultaneously in one reactor or in one bed.Alternatively, the conditions can be controlled such that hydrogenationprimarily occurs in one bed and decarboxylation and/orhydrodeoxygenation occurs in a second bed. Of course if only one bed isused, then hydrogenation occurs primarily at the front of the bed, whiledecarboxylation/hydrodeoxygenation occurs mainly in the middle andbottom of the bed. Finally, desired hydrogenation can be carried out inone reactor, while decarboxylation, decarbonylation, and/orhydrodeoxygenation can be carried out in a separate reactor.

The reaction product from the deoxygenation reactions will comprise botha liquid portion and a gaseous portion. The liquid portion comprises ahydrocarbon fraction which is essentially all n-paraffins and having alarge concentration of paraffins in the range of about 9 to about 18carbon atoms. The gaseous portion comprises hydrogen, carbon dioxide,carbon monoxide, water vapor, propane and perhaps sulfur components suchas hydrogen sulfide or phosphorous component such as phosphine. Theeffluent from the deoxygenation reactor is conducted to a hot highpressure hydrogen stripper. One purpose of the hot high pressurehydrogen stripper is to selectively separate at least a portion of thegaseous portion of the effluent from the liquid portion of the effluent.As hydrogen is an expensive resource, to conserve costs, the separatedhydrogen is recycled to the first reaction zone containing thedeoxygenation reactor. Also, failure to remove the water, carbonmonoxide, and carbon dioxide from the effluent may result in poorcatalyst performance in the isomerization zone. Water, carbon monoxide,carbon dioxide, any ammonia or hydrogen sulfide are selectively strippedin the hot high pressure hydrogen stripper using hydrogen. The hydrogenused for the stripping may be dry, and free of carbon oxides. Thetemperature may be controlled in a limited range to achieve the desiredseparation and the pressure may be maintained at approximately the samepressure as the two reaction zones to minimize both investment andoperating costs. The hot high pressure hydrogen stripper may be operatedat conditions ranging from a pressure of about 689 kPa absolute (100psia) to about 13,790 kPa absolute (2000 psia), and a temperature ofabout 40° C. to about 350° C. In another embodiment the hot highpressure hydrogen stripper may be operated at conditions ranging from apressure of about 1379 kPa absolute (200 psia) to about 4826 kPaabsolute (700 psia), or about 2413 kPa absolute (350 psia) to about 4882kPa absolute (650 psia), and a temperature of about 50° C. to about 350°C. The hot high pressure hydrogen stripper may be operated atessentially the same pressure as the reaction zone. By “essentially”, itis meant that the operating pressure of the hot high pressure hydrogenstripper is within about 1034 kPa absolute (150 psia) of the operatingpressure of the reaction zone. For example, in one embodiment the hothigh pressure hydrogen stripper separation zone is no more than 1034 kPaabsolute (150 psia) less than that of the reaction zone.

The effluent enters the hot high pressure stripper and at least aportion of the gaseous components, are carried with the hydrogenstripping gas and separated into an overhead stream. The remainder ofthe deoxygenation zone effluent stream is removed as hot high pressurehydrogen stripper bottoms and contains the liquid hydrocarbon fractionhaving components such as normal hydrocarbons having from about 8 toabout 24 carbon atoms. Different feedstocks will result in differentdistributions of paraffins. A portion of this liquid hydrocarbonfraction in hot high pressure hydrogen stripper bottoms may be used asthe hydrocarbon recycle described below.

Hydrogen is a reactant in at least some of the reactions above, and asufficient quantity of hydrogen must be in solution to most effectivelytake part in the catalytic reaction. Past processes have operated athigh pressures in order to achieve a desired amount of hydrogen insolution and readily available for reaction. However, higher pressureoperations are more costly to build and to operate as compared to theirlower pressure counterparts. One advantage of the present invention isthe operating pressure may be in the range of about 1379 kPa absolute(200 psia) to about 4826 kPa absolute (700 psia) which is lower thanthat found in other previous operations. In another embodiment theoperating pressure is in the range of about 2413 kPa absolute (350 psia)to about 4481 kPa absolute (650 psia), and in yet another embodimentoperating pressure is in the range of about 2758 kPa absolute (400 psia)to about 4137 kPa absolute (600 psia). Furthermore, the rate of reactionis increased resulting in a greater amount of throughput of materialthrough the reactor in a given period of time. Hydrogen may be separatedfrom process effluent(s) and recycled to the hydrogenation anddeoxygenation zone, or the amount of hydrogen may be in only slightexcess, about 5 to about 25%, of the hydrogen requirements of thehydrogenation and deoxygenation reactions and therefore not recycled.Another refinery unit, such as a hydrocracker, may be used as a sourceof hydrogen, which potentially eliminates the need for a recycle gascompressor

In one embodiment, the desired amount of hydrogen is kept in solution atlower pressures by employing a large recycle of hydrocarbon to thedeoxygenation reaction zone. Other processes have employed hydrocarbonrecycle in order to control the temperature in the reaction zones sincethe reactions are exothermic reactions. However, the range of recycle tofeedstock ratios used herein is determined not on temperature controlrequirements, but instead, based upon hydrogen solubility requirements.Hydrogen has a greater solubility in the hydrocarbon product than itdoes in the feedstock. By utilizing a large hydrocarbon recycle thesolubility of hydrogen in the combined liquid phase in the reaction zoneis greatly increased and higher pressures are not needed to increase theamount of hydrogen in solution. In one embodiment of the invention, thevolume ratio of hydrocarbon recycle to feedstock is from about 2:1 toabout 8:1 or 2:1 to about 6:1. In another embodiment the ratio is in therange of about 3:1 to about 6:1 and in yet another embodiment the ratiois in the range of about 4:1 to about 5:1.

Although the hydrocarbon fraction separated in the hot high pressurehydrogen stripper is useful as a diesel boiling range fuel, because itcomprises essentially n-paraffins, it will have poor cold flowproperties. If it is desired to improve the cold flow properties of theliquid hydrocarbon fraction, then the hydrocarbon fraction can becontacted with an isomerization catalyst under isomerization conditionsto at least partially isomerize the n-paraffins to branched paraffins.The effluent of the second reaction zone, the isomerization zone, is abranched-paraffin-rich stream. By the term “rich” it is meant that theeffluent stream has a greater concentration of branched paraffins thanthe stream entering the isomerization zone, and preferably comprisesgreater than 50 mass-% branched paraffins. It is envisioned that theisomerization zone effluent may contains 70, 80, or 90 mass-% branchedparaffins. Isomerization can be carried out in a separate bed of thesame reaction zone, i.e. same reactor, described above or theisomerization can be carried out in a separate reactor. For ease ofdescription the following will address the embodiment where a secondreactor is employed for the isomerization reaction. The hydrogenstripped product of the deoxygenation reaction zone is contacted with anisomerization catalyst in the presence of hydrogen at isomerizationconditions to isomerize the normal paraffins to branched paraffins. Onlyminimal branching is required, enough to overcome the cold-flow problemsof the normal paraffins. Since attempting for significant branching runsthe risk of high degree of undesired cracking, the predominantisomerized product is a mono-branched hydrocarbon.

The isomerization of the paraffinic product can be accomplished in anymanner known in the art or by using any suitable catalyst known in theart. One or more beds of catalyst may be used. It is preferred that theisomerization be operated in a co-current mode of operation. Fixed bed,trickle bed down flow or fixed bed liquid filled up-flow modes are bothsuitable. See also, for example, US 2004/0230085 A1 which isincorporated by reference in its entirety. Suitable catalysts comprise ametal of Group VIII (IUPAC 8-10) of the Periodic Table and a supportmaterial. Suitable Group VIII metals include platinum and palladium,each of which may be used alone or in combination. The support materialmay be amorphous or crystalline. Suitable support materials includeamorphous alumina, amorphous silica-alumina, ferrierite, ALPO-31,SAPO-11, SAPO-31, SAPO-37, SAPO-41, SM-3, MgAPSO-31, FU-9, NU-10, NU-23,ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, ZSM-57, MeAPO-11,MeAPO-31, MeAPO-41, MeAPSO-11, MeAPSO-31, MeAPSO-41, MeAPSO-46,ELAPO-11, ELAPO-31, ELAPO-41, ELAPSO-11, ELAPSO-31, ELAPSO-41,laumontite, cancrinite, offretite, hydrogen form of stillbite, magnesiumor calcium form of mordenite, and magnesium or calcium form ofpartheite, each of which may be used alone or in combination. ALPO-31 isdescribed in U.S. Pat. No. 4,310,440. SAPO-11, SAPO-31, SAPO-37, andSAPO-41 are described in U.S. Pat. No. 4,440,871. SM-3 is described inU.S. Pat. No. 4,943,424; U.S. Pat. No. 5,087,347; U.S. Pat. No.5,158,665; and U.S. Pat. No. 5,208,005. MgAPSO is a MeAPSO, which is anacronym for a metal aluminumsilicophosphate molecular sieve, where themetal Me is magnesium (Mg). Suitable MeAPSO-31 catalysts includeMgAPSO-31. MeAPSOs are described in U.S. Pat. No. 4,793,984, and MgAPSOsare described in U.S. Pat. No. 4,758,419. MgAPSO-31 is a preferredMgAPSO, where 31 means a MgAPSO having structure type 31. Many naturalzeolites, such as ferrierite, that have an initially reduced pore sizecan be converted to forms suitable for olefin skeletal isomerization byremoving associated alkali metal or alkaline earth metal by ammonium ionexchange and calcination to produce the substantially hydrogen form, astaught in U.S. Pat. No. 4,795,623 and U.S. Pat. No. 4,924,027. Furthercatalysts and conditions for skeletal isomerization are disclosed inU.S. Pat. No. 5,510,306, U.S. Pat. No. 5,082,956, and U.S. Pat. No.5,741,759.

The isomerization catalyst may also comprise a modifier selected fromthe group consisting of lanthanum, cerium, praseodymium, neodymium,samarium, gadolinium, terbium, and mixtures thereof, as described inU.S. Pat. No. 5,716,897 and U.S. Pat. No. 5,851,949. Other suitablesupport materials include ZSM-22, ZSM-23, and ZSM-35, which aredescribed for use in dewaxing in U.S. Pat. No. 5,246,566 and in thearticle entitled “New molecular sieve process for lube dewaxing by waxisomerization,” written by S. J. Miller, in Microporous Materials 2(1994) 439-449. The teachings of U.S. Pat. No. 4,310,440; U.S. Pat. No.4,440,871; U.S. Pat. No. 4,793,984; U.S. Pat. No. 4,758,419; U.S. Pat.No. 4,943,424; U.S. Pat. No. 5,087,347; U.S. Pat. No. 5,158,665; U.S.Pat. No. 5,208,005; U.S. Pat. No. 5,246,566; U.S. Pat. No. 5,716,897;and U.S. Pat. No. 5,851,949 are hereby incorporated by reference.

U.S. Pat. No. 5,444,032 and U.S. Pat. No. 5,608,968 teach a suitablebifunctional catalyst which is constituted by an amorphoussilica-alumina gel and one or more metals belonging to Group VIIIA, andis effective in the hydroisomerization of long-chain normal paraffinscontaining more than 15 carbon atoms. An activated carbon catalystsupport may also be used. U.S. Pat. No. 5,981,419 and U.S. Pat. No.5,908,134 teach a suitable bifunctional catalyst which comprises: (a) aporous crystalline material isostructural with beta-zeolite selectedfrom boro-silicate (BOR-B) and boro-alumino-silicate (Al-BOR-B) in whichthe molar SiO₂:Al₂O₃ ratio is higher than 300:1; (b) one or moremetal(s) belonging to Group VIIIA, selected from platinum and palladium,in an amount comprised within the range of from 0.05 to 5% by weight.Article V. Calemma et al., App. Catal. A: Gen., 190 (2000), 207 teachesyet another suitable catalyst.

The isomerization catalyst may be any of those well known in the artsuch as those described and cited above. Isomerization conditionsinclude a temperature of about 150° C. to about 360° C. and a pressureof about 1724 kPa absolute (250 psia) to about 4726 kPa absolute (700psia). In another embodiment the isomerization conditions include atemperature of about 300° C. to about 360° C. and a pressure of about3102 kPa absolute (450 psia) to about 3792 kPa absolute (550 psia).Other operating conditions for the isomerization zone are well known inthe art. Operating at the low pressures allows for the optionalintroduction of hydrogen from another unit such as a hydrogen plantwithout the use of a make-up compressor which may be an option to reduceor eliminate hydrogen recycle. When hydrogen is not recycled, the amountof hydrogen introduced to the isomerization zone would be only slightlygreater than that which is consumed, an excess of about 5 to about 25percent of the consumption requirements.

The final effluent stream, i.e. the stream obtained after all reactionshave been carried out, is now processed through one or more separationsteps to obtain a purified hydrocarbon stream useful as a diesel fuel.With the final effluent stream comprising both a liquid component and agaseous component, various portions of which are to be recycled,multiple separation steps may be employed. For example, hydrogen may befirst separated in a isomerization effluent separator with the separatedhydrogen being removed in an overhead stream. Suitable operatingconditions of the isomerization effluent separator include, for example,a temperature of 230° C. and a pressure of 4100 kPa absolute (600 psia).If there is a low concentration of carbon oxides, or the carbon oxidesare removed, the hydrogen may be recycled back to the hot high pressurehydrogen stripper for use both as a stripping gas and to combine withthe remainder as a bottoms stream. The remainder is passed to theisomerization reaction zone and thus the hydrogen becomes a component ofthe isomerization reaction zone feed streams in order to provide thenecessary hydrogen partial pressures for the reactor. The hydrogen isalso a reactant in the deoxygenation reactors, and different feedstockswill consume different amounts of hydrogen. The isomerization effluentseparator allows flexibility for the process to operate even when largeramounts of hydrogen are consumed in the first reaction zone.Furthermore, at least a portion of the remainder or bottoms stream ofthe isomerization effluent separator may be recycled to theisomerization reaction zone to increase the degree of isomerization.

The remainder of the final effluent after the removal of hydrogen stillhas liquid and gaseous components and is cooled, by techniques such asair cooling or water cooling and passed to a cold separator where theliquid component is separated from the gaseous component. Suitableoperating conditions of the cold separator include, for example, atemperature of about 20 to 60° C. and a pressure of 3850 kPa absolute(560 psia). A water byproduct stream is also separated. At least aportion of the liquid component, after cooling and separating from thegaseous component, may be recycled back to the isomerization zone toincrease the degree of isomerization. Prior to entering the coldseparator, the remainder of the final effluent stream may be combinedwith the hot high pressure hydrogen stripper overhead stream, and theresulting combined stream may be introduced into the cold separator.

The liquid component contains the hydrocarbons useful as diesel fuel,termed diesel fuel range hydrocarbons, as well as smaller amounts ofnaphtha and LPG. The separated liquid component may be recovered asdiesel fuel or it may be further purified in a product stripper whichseparates lower boiling components and dissolved gases into an LPG andnaphtha stream from the diesel product containing C₈ to C₂₄ normal andbranched alkanes. Suitable operating conditions of the product stripperinclude a temperature of from about 20 to about 200° C. at the overheadand a pressure from about 0 to about 1379 kPa absolute (0 to 200 psia).

The LPG and naphtha stream may be further separated in a debutanizer ordepropanizer in order to separate the LPG into an overhead stream,leaving the naphtha in a bottoms stream. Suitable operating conditionsof this unit include a temperature of from about 20 to about 200° C. atthe overhead and a pressure from about 0 to about 2758 kPa absolute (0to 400 psia). The LPG may be sold as valuable product or may be used inother processes such as a feed to a hydrogen production facility.Similarly, the naphtha may be used in other processes, such as the feedto a hydrogen production facility, a co-feed to a reforming process, ormay be used as a fuel blending component in, for example, the gasolineblending pool.

The gaseous component separated in the product separator comprisesmostly hydrogen and the carbon dioxide from the decarboxylationreaction. Other components such as carbon monoxide, propane, andhydrogen sulfide or other sulfur containing component may be present aswell. It is desirable to recycle the hydrogen to the isomerization zone,but if the carbon dioxide was not removed, its concentration wouldquickly build up and effect the operation of the isomerization zone. Thecarbon dioxide can be removed from the hydrogen by means well known inthe art such as reaction with a hot carbonate solution, pressure swingabsorption, etc. Amine absorbers may be employed as taught in copendingapplications docket number H0013966 and docket number H0017132, herebyincorporated by reference. If desired, essentially pure carbon dioxidecan be recovered by regenerating the spent absorption media.

Similarly, a sulfur containing component such as hydrogen sulfide may bepresent to maintain the sulfided state of the deoxygenation catalyst orto control the relative amounts of the decarboxylation reaction and thehydrogenation reaction that are both occurring in the deoxygenationzone. The amount of sulfur is generally controlled and so must beremoved before the hydrogen is recycled. The sulfur components may beremoved using techniques such as absorption with an amine or by causticwash. Of course, depending upon the technique used, the carbon dioxideand sulfur containing components, and other components, may be removedin a single separation step such as a hydrogen selective membrane.

The hydrogen remaining after the removal of at least carbon dioxide maybe recycled to the reaction zone where hydrogenation primarily occursand/or to any subsequent beds or reactors. The recycle stream may beintroduced to the inlet of the reaction zone and/or to any subsequentbeds or reactors. One benefit of the hydrocarbon recycle is to controlthe temperature rise across the individual beds. However, as discussedabove, the amount of hydrocarbon recycle may be determined based uponthe desired hydrogen solubility in the reaction zone which is in excessof that used for temperature control. Increasing the hydrogen solubilityin the reaction mixture allows for successful operation at lowerpressures, and thus reduced cost.

The following embodiment is presented in illustration of this inventionand is not intended as an undue limitation on the generally broad scopeof the invention as set forth in the claims. First the process isdescribed in general as with reference to FIG. 1. Then the process isdescribed in more detail with reference to FIG. 2.

Turning to FIG. 1 renewable feedstock 102 enters deoxygenation reactionzone 104 along with recycle hydrogen 126. Deoxygenated product 106 isstripped in hot high pressure hydrogen stripper 108 using hydrogen 114a. Carbon oxides and water vapor are removed with hydrogen in overhead110. Selectively stripped deoxygenated product is passed toisomerization zone 116 along with recycle hydrogen 126 a and make-uphydrogen 114 b. Isomerized product 118 is combined with overhead 110 andpassed to product recovery zone 120. Carbon oxide stream 128, light endsstream 130, water byproduct stream 124, hydrogen stream 126, andbranched paraffin-rich product 122 are removed from product recover zone120. Branched paraffin-rich product 122 may be collected for use asdiesel fuel and hydrogen stream 126 is recycled to the deoxygenationreaction zone 104.

Turning to FIG. 2, the process begins with a renewable feedstock stream2 which may pass through an optional feed surge drum. The feedstockstream is combined with recycle gas stream 68 and recycle stream 16 toform combined feed stream 20, which is heat exchanged with reactoreffluent and then introduced into deoxygenation reactor 4. The heatexchange may occur before or after the recycle is combined with thefeed. Deoxygenation reactor 4 may contain multiple beds shown in FIG. 2as 4 a, 4 b and 4 c. Deoxygenation reactor 4 contains at least onecatalyst capable of catalyzing decarboxylation and/or hydrodeoxygenationof the feedstock to remove oxygen. Deoxygenation reactor effluent stream6 containing the products of the decarboxylation and/orhydrodeoxygenation reactions is removed from deoxygenation reactor 4 andheat exchanged with stream 20 containing feed to the deoxygenationreactor. Stream 6 comprises a liquid component containing largely normalparaffin hydrocarbons in the diesel boiling range and a gaseouscomponent containing largely hydrogen, vaporous water, carbon monoxide,carbon dioxide and propane.

Deoxygenation reactor effluent stream 6 is then directed to hot highpressure hydrogen stripper 8. Make up hydrogen in line 10 is dividedinto two portions, stream 10 a and 10 b. Make up hydrogen in stream 10 ais also introduced to hot high pressure hydrogen stripper 8. In hot highpressure hydrogen stripper 8, the gaseous component of deoxygenationreactor effluent 6 is selectively stripped from the liquid component ofdeoxygenation reactor effluent 6 using make-up hydrogen 10 a and recyclehydrogen 28. The dissolved gaseous component comprising hydrogen,vaporous water, carbon monoxide, carbon dioxide and at least a portionof the propane, is selectively separated into hot high pressure hydrogenstripper overhead stream 14. The remaining liquid component ofdeoxygenation reactor effluent 6 comprising primarily normal paraffinshaving a carbon number from about 8 to about 24 with a cetane number ofabout 60 to about 100 is removed as hot high pressure hydrogen stripperbottom 12.

A portion of hot high pressure hydrogen stripper bottoms forms recyclestream 16 and is combined with renewable feedstock stream 2 to createcombined feed 20. Another portion of recycle stream 16, optional stream16 a, may be routed directly to deoxygenation reactor 4 and introducedat interstage locations such as between beds 4 a and 4 b and/or betweenbeds 4 b and 4 c in order, or example, to aid in temperature control.The remainder of hot high pressure hydrogen stripper bottoms in stream12 is combined with hydrogen stream 10 b to form combined stream 18which is routed to isomerization reactor 22. Stream 18 may be heatexchanged with isomerization reactor effluent 24.

The product of the isomerization reactor containing a gaseous portion ofhydrogen and propane and a branched-paraffin-rich liquid portion isremoved in line 24, and after optional heat exchange with stream 18, isintroduced into hydrogen separator 26. The overhead stream 28 fromhydrogen separator 26 contains primarily hydrogen which may be recycledback to hot high pressure hydrogen stripper 8. Bottom stream 30 fromhydrogen separator 26 is air cooled using air cooler 32 and introducedinto product separator 34. In product separator 34 the gaseous portionof the stream comprising hydrogen, carbon monoxide, hydrogen sulfide,carbon dioxide and propane are removed in stream 36 while the liquidhydrocarbon portion of the stream is removed in stream 38. A waterbyproduct stream 40 may also be removed from product separator 34.Stream 38 is introduced to product stripper 42 where components havinghigher relative volatilities are separated into stream 44 with theremainder, the diesel range components, being withdrawn from productstripper 42 in line 46. Stream 44 is introduced into fractionator 48which operates to separate LPG into overhead 50 leaving a naphthabottoms 52. Any of optional lines 72, 74, or 76 may be used to recycleat least a portion of the isomerization zone effluent back to theisomerization zone to increase the amount of n-paraffins that areisomerized to branched paraffins.

The vapor stream 36 from product separator 34 contains the gaseousportion of the isomerization effluent which comprises at least hydrogen,carbon monoxide, hydrogen sulfide, carbon dioxide and propane and isdirected to a system of amine absorbers to separate carbon dioxide andhydrogen sulfide from the vapor stream. Because of the cost of hydrogen,it is desirable to recycle the hydrogen to deoxygenation reactor 4, butit is not desirable to circulate the carbon dioxide or an excess ofsulfur containing components. In order to separate sulfur containingcomponents and carbon dioxide from the hydrogen, vapor stream 36 ispassed through a system of at least two amine absorbers, also calledscrubbers, starting with the first amine absorber zone 56. The aminechosen to be employed in first amine scrubber 56 is capable ofselectively removing at least both the components of interest, carbondioxide and the sulfur components such as hydrogen sulfide. Suitableamines are available from DOW and from BASF, and in one embodiment theamines are a promoted or activated methyldiethanolamine (MDEA). See U.S.Pat. No. 6,337,059, hereby incorporated by reference in its entirety.Suitable amines for the first amine absorber zone from DOW include theUCARSOL™ AP series solvents such as AP802, AP804, AP806, AP810 andAP814. The carbon dioxide and hydrogen sulfide are absorbed by the aminewhile the hydrogen passes through first amine scrubber zone and intoline 68 to be recycled to the first reaction zone. The amine isregenerated and the carbon dioxide and hydrogen sulfide are released andremoved in line 62. Within the first amine absorber zone, regeneratedamine may be recycled for use again. The released carbon dioxide andhydrogen sulfide in line 62 are passed through second amine scrubberzone 58 which contains an amine selective to hydrogen sulfide, but notselective to carbon dioxide. Again, suitable amines are available fromDOW and from BASF, and in one embodiment the amines are a promoted oractivated MDEA. Suitable amines for the second amine absorber zone fromDOW include the UCARSOL™ HS series solvents such as HS101, HS 102,HS103, HS104, HS115. Therefore the carbon dioxide passes through secondamine scrubber zone 58 and into line 66. The amine may be regeneratedwhich releases the hydrogen sulfide into line 60. Regenerated amine isthen reused, and the hydrogen sulfide may be recycled to thedeoxygenation reaction zone. Conditions for the first scrubber zoneincludes a temperature in the range of 30 to 60° C. The first absorberis operated at essentially the same pressure as the reaction zone. By“essentially” it is meant that the operating pressure of the firstabsorber is within about 1034 kPa absolute (150 psia) of the operatingpressure of the reaction zone. For example, the pressure of the firstabsorber is no more than 1034 kPa absolute (150 psia) less than that ofthe reaction zone. The second amine absorber zone is operated in apressure range of from 138 kPa absolute (20 psia) to 241 kPa absolute(35 psia). Also, at least the first the absorber is operated at atemperature that is at least 1° C. higher than that of the separator.Keeping the absorbers warmer than the separator operates to maintain anylight hydrocarbons in the vapor phase and prevents the lighthydrocarbons from condensing into the absorber solvent.

1) A process for producing a branched-paraffin-rich diesel boiling rangehydrocarbon product from a renewable feedstock comprising: a) treatingthe feedstock in a first reaction zone by hydrogenating anddeoxygenating the feedstock using a catalyst at reaction conditions inthe presence of hydrogen to provide a first reaction zone product streamcomprising hydrogen, carbon dioxide, and a hydrocarbon fractioncomprising n-paraffins in the diesel boiling range; and b) selectivelyseparating, in a hot high pressure hydrogen stripper, a gaseous streamcomprising at least a portion of the hydrogen, water, and carbon oxidesfrom the first reaction zone product stream and introducing a remainderstream comprising at least the n-paraffins to a second reaction zone tocontact an isomerization catalyst at isomerization conditions toisomerize at least a portion of the n-paraffins and generate a branchedparaffin-rich stream. 2) The process of claim 1 further comprising: c)combining the branched paraffin-rich stream and the gaseous stream toform a combined stream; d) cooling the combined stream and separating agaseous component comprising at least hydrogen and carbon dioxide from aliquid hydrocarbon component and a water component; and e) recoveringthe liquid hydrocarbon component. 3) The process of claim 1 furthercomprising removing at least a portion of the hydrogen from the branchedparaffin-rich stream. 4) The process of claim 3 further comprisingrecycling the hydrogen removed from the branched paraffin-rich stream tothe hot high pressure hydrogen stripper. 5) The process of claim 2further comprising recycling the gaseous component comprising at leasthydrogen and carbon dioxide to the first reaction zone. 6) The processof claim 1 further comprising recycling a portion of the remainderstream comprising a least the n-paraffins to the first reaction zone ata volume ratio of recycle to feedstock in the range of about 2:1 toabout 8:1. 7) The process of claim 6 wherein the reaction conditions inthe first reaction zone include a temperature of about 40° C. to about400° C. and a pressure of about 689 kPa absolute (100 psia) to about13,790 kPa absolute (2000 psia). 8) The process of claim 2 furthercomprising separating the liquid hydrocarbon component into an LPG andnaphtha stream and a diesel boiling range stream. 9) The process ofclaim 8 further comprising separating the LPG and naphtha stream into anLPG stream and a naphtha stream. 10) The process of claim 9 furthercomprising recycling at least a portion of the naphtha steam to thesecond reaction zone. 11) The process of claim 1 further comprisingrecycling at least a portion of the branched paraffin-rich stream to thesecond reaction zone. 12) The process of claim 1 further comprisingintroducing a make up hydrogen stream to the hot high pressure hydrogenstripper. 13) The process of claim 1 further comprising combining afresh hydrogen stream with the remainder stream. 14) The process ofclaim 1 further comprising pre-treating the feedstock in a pretreatmentzone at pretreatment conditions to remove at least a portion ofcontaminants in the feedstock. 15) The process of claim 1 where thedeoxygenating comprises at least one of decarboxylation,decarbonylation, and hydrodeoxygenation. 16) The process of claim 5further comprising separating carbon dioxide from the gaseous componentstream prior to recycling the gaseous component to the first reactionzone. 17) The process of claim 5 further comprising separatingsulfur-components from the gaseous component stream prior to recyclingthe gaseous component to the first reaction zone. 18) The process ofclaim 1 wherein the first and second reaction zones are operated atconditions including a temperature of about 40° C. to about 400° C. anda pressure of about 689 kPa absolute (100 psia) to about 13,790 kPaabsolute (2000 psia). 19) The process of claim 1 wherein the hot highpressure hydrogen stripper is operated at a temperature of about 40° C.to about 300° C. and a pressure of about 689 kPa absolute (100 psia) toabout 13,790 kPa absolute (2000 psia). 20) The process of claim 1wherein the hot high pressure hydrogen stripper is operated at apressure that is within 1034 kPa absolute (150 psia) that of the firstreaction zone. 21) The process of claim 1 wherein the second reactionzone is operated at a pressure at least 345 kPa absolute (50 psia)greater than that of the first reaction zone. 22) The process of claim 1wherein the renewable feedstock is selected from the group consisting ofcanola oil, corn oil, soy oils, rapeseed oil, soybean oil, colza oil,tall oil, sunflower oil, hempseed oil, olive oil, linseed oil, coconutoil, castor oil, peanut oil, palm oil, mustard oil, cottonseed oil,jatropha oil, tallow, yellow and brown greases, lard, train oil, fats inmilk, fish oil, algal oil, sewage sludge, ratanjoy oil, wild castor oil,jangli oil erandi oil, mohuwa oil, karanji honge oil, neem oil, andmixtures thereof. 23) The process of claim 22 wherein the renewablefeedstock comprises at least one co-feed selected from the groupconsisting of petroleum derived hydrocarbons, spent motor oils,industrial lubricants, used paraffin waxes, liquids derived from thegasification of coal followed by a downstream liquefaction step, liquidsderived from the gasification of biomass followed by a downstreamliquefaction step, liquids derived from the gasification of natural gasfollowed by a downstream liquefaction step, liquids derived from thermalor chemical depolymerization of waste plastics, and synthetic oilsgenerated as byproducts from petrochemical and chemical processes.